Rotary-disc device dynamic filtering

ABSTRACT

The invention concerns a modular dynamic filtering device with rotary discs comprising membranes ( 41, 42, 51, 52 ) arranged on either side of fixed support plates ( 4, 5 ). The modular construction enables the filtering device to be universal and adaptable by the user to be used for different types of filtration from microfiltration to nanofiltration, and even reverse osmosis.

[0001] This invention relates to a modular dynamic filtration devicewith rotary disk(s) comprising diaphragms arranged on either side offixed supporting plates. Modularity enables the polyvalence of thefiltration device according to the invention, which may be adapted bythe user to applications ranging from low pressures to high pressures,above 20 bars, i.e. from microfiltration to nanofiltration, even reverseosmosis.

[0002] Dynamic filtration devices with rotary disks are known for theircapacity to provide high fluxes of permeate and notably greater thanthose obtained with conventional tangential filtration systems, notablyin the case of loaded and pointing fluids. Such modules also enable towork at low pressures through diaphragms in microfiltration, which isinteresting for extracting macromolecules from fermentation worts ormilk worts, whereas the absence or the reduction of deposit facilitatestransmission by the diaphragm.

[0003] Such modules exhibit however the shortcoming of being complex(mobile parts, tightness problems), which translates by cost ofmanufacture vastly higher than conventional systems.

[0004] Moreover, such systems can only be used in a given filtrationfield, for a range of set pressures, generally small.

[0005] Thus, the dynamic separation system DMF marketed by the PALLCompany, comprising filtering stators fitted with diaphragm, separate byrotary disks (or rotors), may only be used at pressures lower than orequal to 3 bars, and not beyond, i.e. solely in microfiltration. Thediaphragms are already assembled on the stators and their assembly anddisassembly is difficult.

[0006] This invention therefore relates to a modular dynamic filtrationdevice with rotary disks, which remedies the shortcomings of theprevious art.

[0007] This invention therefore relates to a modular dynamic filtrationdevice with rotary disk comprising:

[0008] a cylindrical enclosure (E) including:

[0009] a base, a crown and a lid, said lid comprising an upper face anda side wall which may be imbedded in said crown,

[0010] at least two filters F₁ and F₂ dividing the enclosure into atleast three compartments, each of said filters comprising a supportingplate stationary fixed to the enclosure, and two diaphragms arranged oneither side of said supporting plate,

[0011] at least one rotary disk, arranged between two consecutivefilters,

[0012] at least one common device for injecting of a liquid to befiltered, said injection device running through the base of theenclosure, or the upper lid,

[0013] at least one common device for discharging the residue obtainedfrom the liquid to be filtered, said residue discharging device runningthrough an upper face of the lid of the enclosure,

[0014] at least two devices for discharging the filtrate obtained fromthe liquid to be filtered, said devices for discharging the filtraterunning through the crown of the enclosure, and

[0015] a shaft forming the axis of said enclosure carrying the disk(s)and liable to be driven into rotation which drives into rotation therotary disk(s).

[0016] According to the invention, the filtration device is modular, andtwo consecutive supporting plates are separate by a spacer for easierassembly and disassembly, changing the number of compartments, greatertightness and changing the disk-diaphragm space. Besides, the diaphragmsusable according to the invention may be selected among the set of flatmarketable diaphragms which can be used in the following fields:microfiltration, ultrafiltration, nanofiltration and reverse osmosis.

[0017] Advantageously, the supporting plates according to the inventionare in the form of a disk with diameter d₁, and the diaphragms arrangedon either side of a supporting plate according to the invention are alsoin the form of a disk of same diameter (diameter d₁).

[0018] Advantageously, the diameter d₁ varies from 10 to 100 cm.

[0019] Besides, the nature of the rotary disks as well as the spacingbetween each disk and the diaphragm closest to said disk may be adaptedrelative to the liquid to be filtered and its physical features.

[0020] Generally, the spacing between each disk and the diaphragmclosest to said disk ranges between 2 and 20 mm.

[0021] Advantageously, the devices for discharging the filtrate arearranged in the extension of the filters F₁ and F₂ respectively.

[0022] According to a first feature of the invention, the filter is anassembly comprising a supporting plate whereof each face is fitted witha diaphragm and with a drainage layer enabling radial discharge of thefiltrate towards the filtrate discharging device. The drainage layer isgenerally arranged between the face of the supporting plate and thediaphragm.

[0023] Advantageously, a non-woven drainage product shall be used.

[0024] When the filtration module according to the invention is used inmicrofiltration, the flux of permeate is relatively important, generallyof the order of 2 to 10 ?/minute/m² of diaphragm. Consequently, forusage in microfiltration, the supporting plate will be advantageouslyfitted with radial scores for easier discharge of the filtrate.

[0025] According to another feature of the invention, the filter is asingle part made of porous material, sintered or not, preferably ofceramic whereof the porosity increases towards the inside of said part,so that the diaphragms are composed of the faces of said part withlowest porosity, the supporting plate is composed of the central portionof said part with high porosity, and the drainage layers are composed ofthe intermediate portions with average porosity situated between thefaces and the central portion of said part. The filter is preferablymade of ceramic.

[0026] According still to another feature of the invention, the filteris an assembly comprising:

[0027] a supporting plate fitted with at least two ducts with diameterd₂ for lateral discharge of the permeate, and

[0028] two organic or mineral diaphragms arranged on either side of thesupporting plate.

[0029] Advantageously, the ducts are radial and are connected to eachface of the supporting plate by conduits with a diameter smaller thanthat of the ducts.

[0030] The diameter d₃ of the conduits (cf. FIG. 2) is generally smallerthan the diameter d₂ of the ducts. Preferably, the diameter d₂ of theducts is smaller than or equal to 4 mm, and preferably of 0.5 a 3 mm,and the diameter d₃ of the conduits (15) is smaller than or equal to 2mm.

[0031] In a particular embodiment of the invention, the rotary disks arefitted with fins, preferably approximately 6 to 8 in number, and from 2to 8 mm in height.

[0032] The presence of fins on the rotary disks enables:

[0033] for the same rotational speed, to increaser the filtrationperformances relative to the smooth disks thanks to better driving ofthe liquid to be filtered, or

[0034] for performances identical to those obtained with smooth disks,to reduce the rotational speed of the disks and therefore the energynecessary to the implementation of the filtration process.

[0035] The invention also relates to a filter composed of a single partmade of porous material, sintered or not, with variable porosity, asdefined according to one of the claims 11 or 12.

[0036] Finally, the invention also relates to a filter whereof thesupporting plate comprises ducts and of the conduits with diameters asdefined according to one of the claims 13 and 14.

[0037] The invention will be understood better and other aims,advantages and features thereof will appear more clearly when readingthe following description, in conjunction with the appended drawingswhereon:

[0038]FIG. 1 shows a sectional view of an example of dynamic filtrationdevice according to the invention comprising two filters separate by arotary disk.

[0039]FIG. 2 represents schematically three comparative views of filtersusable according to the invention, whereof the one 2A corresponds to oneexample of filter of the previous art and the other two 2B and 2Ccorrespond to two examples of filters according to the invention.

[0040]FIG. 3 represents schematically a horizontal sectional viewaccording to the line I-I of the FIG. 1 of the supporting plate of afilter of the previous art.

[0041]FIG. 4 represents schematically a vertical sectional viewaccording to the line II-II of FIG. 2c of half a supporting plate of afilter according to the invention.

[0042]FIG. 5 represents schematically a lateral perspective view of halfa supporting plate analogue to that represented on FIG. 4.

[0043] On FIG. 1 is represented an example of modular dynamic filtrationdevice according to the invention including a cylindrical enclosure Ecomprising a circular base 1, a cylindrical crown 2 resting on the base1 and enclosed upward by an upper face 31 of a lid 3. The side wall 32of the lid 3 may be imbedded in the crown 2.

[0044] The inside volume of the enclosure is divided into 3 compartments(lower, intermediate and upper) by two filters in the form of stationarydisks F₁, F₂, fixed at their rim outside the crown 2.

[0045] The stationary filters F₁ et F₂ are separate by a rotary disk 6liable to rotate at high speed (4000 t/mn). This rotary disk 6 iscarried by a shaft central 10 forming the axis of the enclosure E. Theshaft 10 is inserted into a central hole in the filters F₁ and F₂. Whenthe shaft 10 carrying the disk 6 is driven into rotation, it drives inturn the disk 6 into rotation.

[0046] The filters F₁ and F₂ separate by a spacer 11 placed in the sidewall 32 of the lid 3 between the outer rims of the filters F₁ and F₂.

[0047] The enclosure E contains two devices for injecting a liquid to beprocessed running through the base 1 of the enclosure E, arrangedsymmetrically on either side of the central shaft 10, so that the liquidto be filtered penetrates between the crown 2, the filter F₁ and thedisk through the central hole.

[0048] The portion of the liquid to be filtered running through thefilter F₁ is the filtrate Fa₁.

[0049] The filtrate Fa₁ is discharged laterally from the filter F₁ tothe outside of the enclosure E, through a first discharging device 91situated in the extension of the filter F₁ and running through the crown2 of the enclosure E.

[0050] The portion of the liquid to be filtered which has not flownthrough the filter F₁, and which has by-passed such filter F₁ is thencollected in the intermediate compartment delineated by the filter F₂and the disk.

[0051] The filters F₁ and F₂ are separate by the rotary disk 6. Inoperation, the disk 6 rotates at high speed (4000 t/mn) in order toproduce high shearing effect on the diaphragms, which prevents theformation of deposits on the diaphragms, notably during the filtrationof concentrated particle suspensions.

[0052] Identically to the filter F₁, the portion of the liquid to befiltered retained by the filter F₂ is the filtrate Fa₂.

[0053] The filtrate Fa₂ entering the filter F₁ is discharged laterallythrough a second lateral discharging device 92 situated in the extensionof the filter F₂.

[0054] The portion of the liquid to be filtered which has not beenfiltered by both filters F₁ and F₂ form the residue.

[0055] The residue is eliminated for example through a dischargingdevice 8, running through an upper face of the lid 3 of the enclosure E.

[0056] On FIG. 2, representing schematically 3 filters usable accordingto the invention, are compared the structure of a filter of the previousart (diagram A) and those of two filters according to the invention(diagrams B and C).

[0057] The diagram A of the FIG. 2 shows a filter of the previous artcomprising a supporting plate 4, possibly fitted with radial scores(according to FIG. 3), on the faces thereof are arranged successively adrainage layer 12 and, a diaphragm 41, 42.

[0058] The diagram B of FIG. 2 represents schematically an example offilter according to the invention composed of a single part made ofporous sintered material whereof the porosity increases towards theinside of said part. The diaphragms 41, 42 are composed of the faces ofsaid part, since these are the portions of the part with the lowestporosity. The supporting plate (4, 5) is composed of the central portionof said part, since this portion of the part exhibits high porosity.Indeed, the drainage layers are composed of the intermediate portionswith average porosity situated between the faces and the central portionof said part. The size of the pores varies from 0.1 nm to 5 μm accordingto whether it is reverse osmosis or microfiltration.

[0059] The diagram C of FIG. 2 as well as FIGS. 4 and 5 representschematically another example of filter according to the inventioncomposed of a supporting plate fitted with radial channels with diameterd₂ connected to the faces of the supporting plate by conduits withdiameters d₃, smaller than d₂.

1. A rotary disk dynamic filtration device comprising: a cylindricalenclosure (E) including: a base (1), a crown (2) and a lid (3), said lid(3) comprising an upper face (31) and a side wall (32) may be imbeddedinto said crown. (2), at least two filters F₁ and F₂ dividing theenclosure into at least three compartments, each of said filterscomprising a supporting plate (4, 5) stationary fixed to the enclosure(E), and two diaphragms (41, 42, 51, 52) arranged on either side of thesupporting plate (4, 5) at least one rotary disk (6) arranged betweentwo consecutive filters, at least one common device for injecting (7) ofa liquid to be filtered, said injection device (7) running througheither the base (1) of the enclosure E, or the lid (3), at least onecommon device for discharging (8) the residue obtained from the liquidto be filtered, said residue discharging device (8) running through theupper face of the lid (3) of the enclosure E or the base (1), at leasttwo devices for discharging (91, 92) the filtrate obtained from theliquid to be filtered, said discharging devices (9) running through thecrown (2) of the enclosure (E), a shaft (10) forming the axis of saidenclosure (E) carrying the disk(s) (6) and liable to be driven intorotation, characterised in that it is modular, and also characterised inthat: two supporting consecutive plates (4, 5) are separate by a spacer(11) for easier assembly and disassembly, changing the number ofcompartments, greater tightness and changing the disk-diaphragm space,the diaphragms are selected among microfiltration diaphragms,ultrafiltration diaphragms, nanofiltration diaphragms and reverseosmosis diaphragms.
 2. A filtration device according to claim 1,characterised in that each supporting plate (4, 5) and the diaphragms(41, 42, 51, 52) arranged on either side of said supporting plate (4, 5)are in the form of a disk.
 3. A filtration device according to claim 1or 2, characterised in that the filter is an assembly comprising asupporting plate (4, 5) whereof each face is fitted with a diaphragm(41, 42, 51, 52) and a drainage layer (12) arranged between the face ofthe supporting plate (4, 5) and the diaphragm (41, 42, 51, 52).
 4. Afiltration device according to claim 3, characterised in that thedrainage product (12) is non woven.
 5. A filtration device according toany of the previous claims, characterised in that the supporting plateis fitted with radial scores (13) to discharge said permeate.
 6. Afiltration device according to claim 1 or 2, characterised in that thefilter is a single part made of porous material, sintered or not,whereof the porosity increases towards the inside of said part, so thatthe diaphragms (41, 42, 51, 52) are composed of the faces of said partwith lowest porosity, the supporting plate (4, 5) is composed of thecentral portion of said part with high porosity, and the drainage layersare composed of the intermediate portions with average porosity situatedbetween the faces and the central portion of said part.
 7. A filtrationdevice according to claim 6, characterised in that the filter consistsof ceramic.
 8. A filtration device according to claim 1 or 2,characterised in that the filter is an assembly comprising: a supportingplate (4, 5), fitted with at least two ducts (14) with diameter d₂ forlateral discharge of the permeate, and two organic or mineral diaphragms(41, 42, 51, 52) arranged on either side of the supporting plate (4, 5).9. A filtration device according to claim 8, characterised in that theducts (14) are radial and are connected to each face of the supportingplate (4, 5) by conduits (15) with diameter d₃ smaller than the diameterd₂ of the ducts (14).
 10. A filtration device according to any of theprevious claims, characterised in that the disk (6) is fitted with fins(16).
 11. A filter including a supporting plate (4, 5) and twodiaphragms (41, 42, 51, 52) arranged on either side of said supportingplate (4, 5), characterised in that the filter is a single part made ofporous material, sintered or not, whereof the porosity increases towardsthe inside of said part, so that the diaphragms (41, 42, 51, 52) arecomposed of the faces of said part with lowest porosity, the supportingplate (4, 5) is composed of the central portion of said part with highporosity, and the drainage layers are composed of the intermediateportions with average porosity situated between the faces and thecentral portion of said part.
 12. A filter according to claim 11,characterised in that the filter consists of ceramic.
 13. A filterincluding a supporting plate (4, 5) and two diaphragms (41, 42, 51, 52)arranged on either side of the supporting plate (4, 5), characterised inthat the supporting plate (4, 5) is fitted with at least two ducts (14)for lateral discharge of the permeate.
 14. A filter according to claim13, characterised in that the ducts (14) are radial, and are connectedto each face of the supporting plate (4, 5) by conduits (15).